Hyun-boo Lee | University of Washington (original) (raw)
Papers by Hyun-boo Lee
International Journal of Precision Engineering and Manufacturing, 2017
RSC advances, 2013
Electric detection using a nanocomponent may lead to platforms for rapid and simple biosensing. S... more Electric detection using a nanocomponent may lead to platforms for rapid and simple biosensing. Sensors composed of nanotips or nanodots have been described for highly sensitive amperometry enabled by confined geometry. However, both fabrication and use of nanostructured sensors remain challenging. This paper describes a dendritic nanotip used as an amperometric biosensor for highly sensitive detection of target bacteria. A dendritic nanotip is structured by Si nanowires coated with single-walled carbon nanotubes (SWCNTs) for generation of a high electric field. For reliable measurement using the dendritic structure, Si nanowires were uniformly fabricated by ultraviolet (UV) lithography and etching. The dendritic structure effectively increased the electric current density near the terminal end of the nanotip according to numerical computation. The electrical characteristics of a dendritic nanotip with additional protein layers was studied by cyclic voltammetry and I-V measurement in deionized (DI) water. When the target bacteria dielectrophoretically captured onto a nanotip were bound with fluorescence antibodies, the electric current through DI water decreased. Measurement results were consistent with fluorescence- and electron microscopy. The sensitivity of the amperometry was 10 cfu/sample volume (10(3) cfu/mL), which was equivalent to the more laborious fluorescence measurement method. The simple configuration of a dendritic nanotip can potentially offer an electrolyte-free detection platform for sensitive and rapid biosensors.
Nanotechnology, 2013
Rapid and sensitive detection of low-abundance viral particles is strongly demanded in health car... more Rapid and sensitive detection of low-abundance viral particles is strongly demanded in health care, environmental control, military defense, and homeland security. Current detection methods, however, lack either assay speed or sensitivity, mainly due to the nanosized viral particles. In this paper, we compare a dendritic, multi-terminal nanotip ('dendritic nanotip') with a single terminal nanotip ('single nanotip') for dielectrophoretic (DEP) concentration of viral particles. The numerical computation studies the concentration efficiency of viral particles ranging from 25 to 100 nm in radius for both nanotips. With DEP and Brownian motion considered, when the particle radius decreases by two times, the concentration time for both nanotips increases by 4-5 times. In the computational study, a dendritic nanotip shows about 1.5 times faster concentration than a single nanotip for the viral particles because the dendritic structure increases the DEP-effective area to overcome the Brownian motion. For the qualitative support of the numerical results, the comparison experiment of a dendritic nanotip and a single nanotip is conducted. Under 1 min of concentration time, a dendritic nanotip shows a higher sensitivity than a single nanotip. When the concentration time is 5 min, the sensitivity of a dendritic nanotip for T7 phage is 10(4) particles ml(-1). The dendritic nanotip-based concentrator has the potential for rapid identification of viral particles.
The Analyst, 2013
A single-step concentration and elution method is developed for detection of DNA in buffer, saliv... more A single-step concentration and elution method is developed for detection of DNA in buffer, saliva, and blood. A nanotip capturing DNA using an electric field and capillary action is directly dissolved in buffer for qPCR analysis. The concentration yield and the relative parameters are compared with those of a commercial kit.
Journal of Fluids and Structures, 2012
ABSTRACT Flow-induced vibration (FIV) by vortex shedding behind a submerged cylinder can lead to ... more ABSTRACT Flow-induced vibration (FIV) by vortex shedding behind a submerged cylinder can lead to damage of nuclear components. With respect to such a serious scenario, various experiments and numerical simulations have been conducted to predict the vibration phenomena. Especially in simulation, the immersed finite element method (IFEM) is a promising approach to solve fluid-structure interaction problems because it needs less computational resources. In this paper, two-dimensional motions of cylinders are simulated by using IFEM to obtain their vibration characteristics. Three benchmark tests such as flow past a fixed circular cylinder, in-line oscillation of a circular cylinder and flow-induced vibration with uni-directional motion are performed to verify the proposed numerical method. Furthermore, bi-directional motions of two horizontally and vertically arranged cylinders as well as that of a single cylinder in fluid flow are analyzed, and then key findings are fully discussed.
Metals and Materials International, 2013
ABSTRACT Many surface finish methods are used to connect a substrate with the electric components... more ABSTRACT Many surface finish methods are used to connect a substrate with the electric components of IT products in the micro-packaging process, and various types of lead-free solder have been developed as alternative materials to lead-based solder to reduce environmental contamination. However, there has been little research on the mechanical properties of the inter-metallic surface which is generated in the bumping process between the lead-free solder and surface films such as Ni/Au. The present work is to derive the material properties of a Ni/Au inter-metallic surface with SAC305 solder. A series of indentation tests were carried out by changing four nano-scale indentation depths and two strain rates. Also, a reverse algorithm method was adopted to determine the elastic-plastic stress-strain curve based on the load-displacement curve from the indentation test data. As a result of the material characterization effort, the mean elastic modulus, yield strength and strain hardening exponent of IMC with Ni/Au finish were determined.
Microfluidics and …, Jan 1, 2012
Microfluidics and …, Jan 1, 2011
Abstract Microscale bioreactors are an important tool in performing bioassays. The speed and effi... more Abstract Microscale bioreactors are an important tool in performing bioassays. The speed and efficiency of these devices is often limited by the rate of reagent mixing. In spite of the various micromixing approaches, the coupled mixing/reaction process has yet to be ...
AIP Conference …, Jan 1, 2010
Recently, the reliability assurance of lead‐free solder to prevent environmental contamination is... more Recently, the reliability assurance of lead‐free solder to prevent environmental contamination is quite important issue for chip‐scale packaging. Although lots of efforts have been devoted to the solder undergone drop, shear and creep loads, there was a little research on IMC ...
International Journal of Precision Engineering and Manufacturing, 2017
RSC advances, 2013
Electric detection using a nanocomponent may lead to platforms for rapid and simple biosensing. S... more Electric detection using a nanocomponent may lead to platforms for rapid and simple biosensing. Sensors composed of nanotips or nanodots have been described for highly sensitive amperometry enabled by confined geometry. However, both fabrication and use of nanostructured sensors remain challenging. This paper describes a dendritic nanotip used as an amperometric biosensor for highly sensitive detection of target bacteria. A dendritic nanotip is structured by Si nanowires coated with single-walled carbon nanotubes (SWCNTs) for generation of a high electric field. For reliable measurement using the dendritic structure, Si nanowires were uniformly fabricated by ultraviolet (UV) lithography and etching. The dendritic structure effectively increased the electric current density near the terminal end of the nanotip according to numerical computation. The electrical characteristics of a dendritic nanotip with additional protein layers was studied by cyclic voltammetry and I-V measurement in deionized (DI) water. When the target bacteria dielectrophoretically captured onto a nanotip were bound with fluorescence antibodies, the electric current through DI water decreased. Measurement results were consistent with fluorescence- and electron microscopy. The sensitivity of the amperometry was 10 cfu/sample volume (10(3) cfu/mL), which was equivalent to the more laborious fluorescence measurement method. The simple configuration of a dendritic nanotip can potentially offer an electrolyte-free detection platform for sensitive and rapid biosensors.
Nanotechnology, 2013
Rapid and sensitive detection of low-abundance viral particles is strongly demanded in health car... more Rapid and sensitive detection of low-abundance viral particles is strongly demanded in health care, environmental control, military defense, and homeland security. Current detection methods, however, lack either assay speed or sensitivity, mainly due to the nanosized viral particles. In this paper, we compare a dendritic, multi-terminal nanotip ('dendritic nanotip') with a single terminal nanotip ('single nanotip') for dielectrophoretic (DEP) concentration of viral particles. The numerical computation studies the concentration efficiency of viral particles ranging from 25 to 100 nm in radius for both nanotips. With DEP and Brownian motion considered, when the particle radius decreases by two times, the concentration time for both nanotips increases by 4-5 times. In the computational study, a dendritic nanotip shows about 1.5 times faster concentration than a single nanotip for the viral particles because the dendritic structure increases the DEP-effective area to overcome the Brownian motion. For the qualitative support of the numerical results, the comparison experiment of a dendritic nanotip and a single nanotip is conducted. Under 1 min of concentration time, a dendritic nanotip shows a higher sensitivity than a single nanotip. When the concentration time is 5 min, the sensitivity of a dendritic nanotip for T7 phage is 10(4) particles ml(-1). The dendritic nanotip-based concentrator has the potential for rapid identification of viral particles.
The Analyst, 2013
A single-step concentration and elution method is developed for detection of DNA in buffer, saliv... more A single-step concentration and elution method is developed for detection of DNA in buffer, saliva, and blood. A nanotip capturing DNA using an electric field and capillary action is directly dissolved in buffer for qPCR analysis. The concentration yield and the relative parameters are compared with those of a commercial kit.
Journal of Fluids and Structures, 2012
ABSTRACT Flow-induced vibration (FIV) by vortex shedding behind a submerged cylinder can lead to ... more ABSTRACT Flow-induced vibration (FIV) by vortex shedding behind a submerged cylinder can lead to damage of nuclear components. With respect to such a serious scenario, various experiments and numerical simulations have been conducted to predict the vibration phenomena. Especially in simulation, the immersed finite element method (IFEM) is a promising approach to solve fluid-structure interaction problems because it needs less computational resources. In this paper, two-dimensional motions of cylinders are simulated by using IFEM to obtain their vibration characteristics. Three benchmark tests such as flow past a fixed circular cylinder, in-line oscillation of a circular cylinder and flow-induced vibration with uni-directional motion are performed to verify the proposed numerical method. Furthermore, bi-directional motions of two horizontally and vertically arranged cylinders as well as that of a single cylinder in fluid flow are analyzed, and then key findings are fully discussed.
Metals and Materials International, 2013
ABSTRACT Many surface finish methods are used to connect a substrate with the electric components... more ABSTRACT Many surface finish methods are used to connect a substrate with the electric components of IT products in the micro-packaging process, and various types of lead-free solder have been developed as alternative materials to lead-based solder to reduce environmental contamination. However, there has been little research on the mechanical properties of the inter-metallic surface which is generated in the bumping process between the lead-free solder and surface films such as Ni/Au. The present work is to derive the material properties of a Ni/Au inter-metallic surface with SAC305 solder. A series of indentation tests were carried out by changing four nano-scale indentation depths and two strain rates. Also, a reverse algorithm method was adopted to determine the elastic-plastic stress-strain curve based on the load-displacement curve from the indentation test data. As a result of the material characterization effort, the mean elastic modulus, yield strength and strain hardening exponent of IMC with Ni/Au finish were determined.
Microfluidics and …, Jan 1, 2012
Microfluidics and …, Jan 1, 2011
Abstract Microscale bioreactors are an important tool in performing bioassays. The speed and effi... more Abstract Microscale bioreactors are an important tool in performing bioassays. The speed and efficiency of these devices is often limited by the rate of reagent mixing. In spite of the various micromixing approaches, the coupled mixing/reaction process has yet to be ...
AIP Conference …, Jan 1, 2010
Recently, the reliability assurance of lead‐free solder to prevent environmental contamination is... more Recently, the reliability assurance of lead‐free solder to prevent environmental contamination is quite important issue for chip‐scale packaging. Although lots of efforts have been devoted to the solder undergone drop, shear and creep loads, there was a little research on IMC ...